Self-pulsing circuit



Patented Dec. 25, 1945 SELF-PULSING CIRCUIT Marvin Chodorow, New York, N. Y., assignor to Maguire Industries, Incorporated, a corpora.-

tion of New York Application August 23, 1943, Serial No. 499,719

3 Claims.

My invention relates to a self-pulsing circuit, and more particularly a self-pulsing circuit in which a thermionic tube, as a magnetron tube, is periodically caused to conduct to produce the pulses. The invention also relates to the method of controlling the timing and voltage of the pulses.

One object of the invention is the production of repetitive pulses of current without the use of moving mechanical parts. A further object is the provision of means for controlling the timing, duration and intensity of the pulses. Qther objects and advantages of the invention will be apparent upon considering the present specification in connection with the accompanying drawing, wherein:

Figure 1 is a diagrammatic illustration of a circuit embodying one form of the invention, and

Figure 2 is a diagrammatic illustration of another form of the invention.

Accordin to the invention the self-pulsing cir-- cuit comprises a magnetron tube, means for influencing the conducting of the tube, and means for causing the tube to conduct.

In the embodiment of the invention illustrated in Figure 1, there is shown a circuit II), in which a magnetron tube II and a condenser I2 are connected. As here shown, the magnetron tube and the condenser are connected in parallel iii the circuit II).

For simplicity of illustration, the magnetron tube is shown without the usual glass envelope. The magnetron tube comprises a filament cathode I3, connected across the terminals of a battery I4, and also connected at one end to thecircuit I0. The. cathode is surrounded by a cylindrical anode I5, which is connected to the circuit III. If the circuit III creates a difference of potential between the cathode I3 and the anode I5, the magnetron tube will ordinarily conduct; that is to say, a discharge of current will take placebotween the cathode I3 and the anode I5, and current will thus flow in the circuit IIJ. Such voltage may be provided by charging the condenser I2. However, the magnetron. tube may be prevented from conducting.

As is well known, conducting of a cathodeanode tube of. anykind may be influenced by a magnetic field appropriately applied to the tube. In the embodiment of the invention illustrated in Figure 1, a separate magnet I6, excited by a winding I1, unrelated to the circuitv I0, is associated with the tube II for influencing the conducting of the tube. In the present instance, the magnet I6 is positioned with its field direction substantially at right angles to the direction of the electron path. In other words the axis of the magnet is substantially parallel to that of the cathode. Furthermore, the magnitude of the magnetic field parallel to the cathode I3 will determine the magnitude of the voltage required to cause the tube to conduct. From the foregoing it will be evident that when the condenser I2 builds up suificient voltage, it will discharge through the tube I I causing it to conduct. In order that the tube may conduct, the condenser must impress upon the tube sufficient voltage to overcome the opposition provided by the field of the magnet I6. Thus, the stronger the field of the magnet IS, the higher will be the voltage at which the tube II conducts.

In order thatthe pulses may not be merely coincident with the initial discharge of the condenser I2, and therefore of but instantaneous duration, a second electro-magnet I8 is provided. The windings IQ of the electro-magnet I8 form a part of the circuit I0, and are connected in series with the magnetron tube II. The magnet I8 is preferably coaxial with the magnet I6, and is so wound that when the tube conducts its field opposes the field of the separate magnet.-

Clearly the magnet I6 and. the magnet I8 may be opposite poles of the same magnet- Operation of the circuit as so far described is as follows: As the condenser I2 charges, the voltage across the magnetron tube I I builds up. Conducting of the tube, however, is opposed by the field. of the magnet I6. Thus the strength of the field generated. by the magnet I6 determines the voltage at which the tube conducts, and hence the voltage of the pulse. As the condenser continues to charge, the voltage across the tube finally overcomes the opposition of the field produced by the magnet I6. Thereupon the tube conducts.

When the tube II conducts the condenser I2 discharges and a pulse of current flows in the circuit I0. Because of the instant drop in voltage across the condenser as it discharges, this pulse of current would be quenched. immediately by the field of the magnet I6 were not means provided. for prolonging its duration. The magnet I8 provides such means. Since the winding of the magnet I8 is in series with the tube. I I, conducting of the tube II energizes the magnet I8; and since the magnet I8 is wound so that its field opposes that of the magnet IS, the resultant magnetic field offers less opposition to conducting of the tube. A lower voltage is thus required to cause the tube II to continue to conduct. Therefore, the condenser I2 continues to discharge until the voltage across the tube drops to a value.

which will not overcome the resultant reduced magnetic field. Thereupon the tube II is quenched, current ceases to flow in the circuit, the field of the magnet I8 drops to zero, and the voltage required to cause the tube to conduct resumes its original value.

A variable resistance 20 is interposed between V the condenser l2 and the magnetron tube II.

A second variable resistance 2| is included in the shunt in which the condenser I2 is connected; and a third variable resistance 22 is "winding opposing action of said separately exinterposed between the source of E. M. F. (not shown) and the shunt containing the condenser.

By suitable choice of the resistances 20, 2! and 22, the condenser l2, the magnitude of the magnetic field, and the tube current (all in accordance with well-known electrical principles) it is possible to determine the duration of the pulses and the interval between pulses.

. A secondary variable condenser 23 and a suitable resistance 24 are connected in parallel in the circuit between the electro-magnet l8 and the shunt containing the condenser 12. The variable condenser 23 is so adjusted that it will provide approximate series resonance in the circuit so that the voltage drop across the winding IQ of the magnet I8, which leads the current, will not extinguish the tube ll before the field of the magnet I8 is established. The resistance 24 is a leakage resistor for discharging the condenser 23 after each pulse has left it charged.

Figure 2 illustrates another embodiment of the invention wherein the winding I9 of the magnet I8 is included in the shunt containing the condenser I2. In this embodiment the winding I9 causes a somewhat different action by the'magnet 18 than that of the corresponding magnet in Figure 1. While the condenser I2 is charging the field induced by the winding I9 augments that of the separate magnet [6. While the condenser l2 discharges, however, the field induced by the winding 19 opposes that of the separate magnet IS.

The present invention provides a simple and effective self-pulsing circuit wherein the pulses are created without moving parts and wherein the timing and voltage of the pulses may be easily adjusted to meet desired conditions.

' The particular embodiments of the invention here described and illustrated are presented merely to indicate how the invention may be applied. Although the invention is particularly described as employing a magnetron tube, clearly other types of thermionic tubes may replace the magnetron tube. Other forms of the invention differing in detail but not in principle from those here described will readily suggest themselves to these familiar with such circuits.

I claim:

1. A self-pulsing circuit comprising a cathodeanode tube, an external circuit between the anode and the cathode of said tube, and a condenser and a variable resistance in series connected in parallel with said tube in said external circuit, in combination with an electro-magnetic winding connected in series with said tube in said external circuit, said winding being disposed adjacent said tube with its axis substancited winding when said tube conducts to lower the voltage at which said tube conducts and thereby lengthen the resulting pulse.

2, itself-pulsing circuit comprising a magnetron tube, an external circuit between the anode and the filament of said tube, said filament being elongated, and a condenser and a variable resistance in series connected in parallel with said tube in said external circuit, in combination with an electro-magnetic winding connected in series with said tube in said external circuit, said winding being disposed adjacent said tube with its axis substantially coaxial with the filament of said tube, and a separately and continuously excited electromagnetic winding also disposed with its axis substantially coaxial with the filament of said tube, said separately excited winding being turned oppositely to said first-named winding, said condenser periodically discharging to cause said tube to .conduct, said separately excited winding continuously opposing conducting of said tube, and said first-named winding opposing action of said separately excited winding when said tube conducts to lower the voltage at which said tube conducts and thereby lengthen the resulting pulse.

3. A self-pulsing circuit comprising a cathodeanode tube, an external circuit between the anode and the cathode of said tube, and a condenser and a variable resistance in series connected in parallel with said tube in said external circuit, in combination with an electro-magnetic winding connected in series with said tube in said external circuit, said winding being disposed adjacent said tube with its axis substantially at right angles to the direction of the electron path, a separately and continuously excited electromagnetic winding also disposed with its axis substantially at right angles to the direction of the electron path, said separately excited winding being turned oppositely to said first-named winding, and a unit comprising a second condenser and a resistance in parallel with said second condenser, said unit being connected in said external circuit in series with said firstnamed winding, said condenser periodically discharging to cause said tube to conduct, said separately excited winding continuously opposing conducting of said tube, said first-named winding opposing action of said separately excited winding when said tube conducts to lower the voltage at which said tube conducts and thereby lengthen the resulting pulse, and said unit preventing said tube from being extinguished before the field of said first-named winding is built up.

MARVIN CHODOROW. 

